The present invention relates to irrigation systems, and more particularly, to an improved filter screen assembly for diaphragm-type irrigation control valves.
The use of valve controlled pressurized irrigation systems for supplying water for the irrigation of plants is extensive throughout the world today. One of the most prevalent systems, particularly for lawn areas and athletic fields, includes a plurality of sprinklers positioned for distributing water over the surface of a land area. One or more control valves connect and disconnect water from a pressurized main supply line to branch lines each typically having several sprinklers connected thereto.
Commercial, municipal and golf course irrigation systems increasingly rely on alternative water sources including reclaimed water. This trend has been prompted by a need to conserve water in many parts of the country. Other water sources used for irrigation include lakes, reservoirs, wells, and the like. However, since water from these sources often contains dirt, sand and other particles and debris, its use has brought with it an increase in the incidence of clogging of various components of irrigation systems. While the most readily apparent solution is to filter the water before it enters the irrigation system, the cost of stand-alone filters, and their maintenance, limits the degree of filtering that is economically feasible.
The problem of clogging in irrigation systems is most acute in portions of the system where water must pass into and around small spaces and through small openings. Small openings occur, for example, in irrigation systems having pilot operated and pressure responsive control valves, pressure regulating valves, in drip systems, and in other low flow irrigation configurations. Another area where dirt and debris cause problems is where the water comes into contact with moving parts. One example where such problems occur is in small solenoid operated plunger valves which have a small valve seal on the end of a plunger which extends into a water passage and acts as a pilot valve.
Pressure responsive and pressure regulating valves used in irrigation systems typically have a main diaphragm valve that is normally pilot operated. Upstream or inlet water pressure passes via a small metering orifice to the back side of the main diaphragm assembly to apply valve closing pressure. The water is vented from the back side of the diaphragm valve via a small pilot valve passage controlled by a solenoid operated pilot valve to the main outlet passage of the valve. Hydraulically actuated diaphragm valves also vent water pressure from the downstream side of the diaphragm, without the need for a solenoid. The small metering orifice through the main diaphragm assembly can become clogged, thereby causing valve failure. The small pilot valve passage can also become clogged with dirt and other debris and impair proper operation of a diaphragm valve.
The pilot valve of an electrically controlled diaphragm valve is normally operated by a plunger of a solenoid that moves back and forth in a bore in a housing surrounded by a coil with the valve seal being an elastomeric disc on the end of the plunger which selectively engages a valve seat. The water controlled by the pilot valve typically flows around and frequently along between the pilot valve plunger and its housing either during pressurization or venting of the control valve. Dirt and debris in the water frequently jam between the plunger and its housing preventing its normal operation. Sealing around or between the plunger and its housing is difficult because the plunger must be free to move and air or other fluids must be free to move in and out of the bore along the plunger.
Accordingly, there is a need for an irrigation control valve with a built-in filter to protect its metering orifice, pilot valve, solenoid, venting passages and other delicate components from clogging and contamination.